William Harnisch Peconic Partners
William Harnisch is the founder of Peconic Partners, a concentrated investment firm known for high-conviction equity positions. The firm’s portfolio often differs sharply from broad market benchmarks, reflecting a willingness to concentrate capital. Harnisch’s disclosures are tracked by investors interested in bold, research-driven concentration.
Top Buys
| Rank | Stock | Value |
|---|---|---|
| 1 |
Dycom Industries
DY
|
+$144M |
| 2 |
AMC Entertainment Holdings
AMC
|
+$49.9M |
| 3 |
Freeport-McMoran
FCX
|
+$38.6M |
| 4 |
MasTec
MTZ
|
+$38.2M |
| 5 |
Cinemark Holdings
CNK
|
+$23.8M |
Top Sells
| Rank | Stock | Value |
|---|---|---|
| 1 |
Amazon
AMZN
|
+$199M |
| 2 |
Quanta Services
PWR
|
+$196M |
| 3 |
First Solar
FSLR
|
+$77.9M |
Sector Composition
| Rank | Sector | Weight |
|---|---|---|
| 1 | Industrials | 89.2% |
| 2 | Miscellaneous | 6.5% |
| 3 | Materials | 3.06% |
| 4 | Communication Services | 1.24% |
| 5 | Consumer Discretionary | 0% |
| Name | Market Value | Portfolio Weight | Shares or Principal |
Change in Stake | Capital Flow | Held Since | |
|---|---|---|---|---|---|---|---|
|
1
Quanta Services
PWR
$95B
| $3.4B | 42.25% |
4,720,847
-286,993
| -6% | -$196M |
2018 Q1
33 quarters
|
|
|
2
Dycom Industries
DY
$7.65B
| $2.25B | 27.92% |
4,443,320
+330,000
| +8% | +$144M |
2013 Q2
52 quarters
|
|
|
3
MasTec
MTZ
$15.3B
| $1.53B | 19.02% |
3,678,431
+100,000
| +3% | +$38.2M |
2025 Q3
3 quarters
|
|
4
PUT
State Street SPDR S&P 500 ETF Trust
SPY
$806B
| $523M | 6.5% |
+700,000
| New | +$508M |
2026 Q2
0 quarters
|
|
|
5
Freeport-McMoran
FCX
$100B
| $246M | 3.06% |
3,917,068
+600,000
| +18% | +$38.6M |
2025 Q4
2 quarters
|
|
|
6
AMC Entertainment Holdings
AMC
$2.6B
| $60.8M | 0.76% |
32,000,000
+29,000,000
| +967% | +$49.9M |
2025 Q3
3 quarters
|
|
|
7
Cinemark Holdings
CNK
$4.46B
| $38.1M | 0.47% |
1,201,917
+801,917
| +200% | +$23.8M |
2025 Q4
2 quarters
|
|
8
Alphabet (Google) Class A
GOOGL
$4.17T
| $643K | 0.01% |
1,800
| – | – |
2025 Q2
4 quarters
|
|
|
9
Amazon
AMZN
$2.7T
| – | – |
-953,414
| Closed | -$199M | – |
|
|
10
First Solar
FSLR
$18.6B
| – | – |
-395,000
| Closed | -$77.9M | – |
|
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William Harnisch's Q2 2026 Portfolio in Review
As of Q2 2026, William Harnisch held 10 positions worth $8.04B, up 39% from $5.78B the previous quarter. Its ten largest holdings account for 100% of the portfolio.
William Harnisch's Q2 2026 filing shows 1 new, 5 increased, 1 reduced and 2 closed positions. The largest sale was Amazon, an estimated $199M.
By sector, the portfolio is most concentrated in Industrials at 89% of assets, down from 92% a quarter earlier, followed by Miscellaneous and Materials.
- William Harnisch added most to Dycom Industries in Q2 2026, an estimated $144M increase.
- William Harnisch's biggest Q2 2026 reduction was Quanta Services, cutting an estimated $196M.
- William Harnisch fully exited Amazon in Q2 2026, selling an estimated $199M.
- William Harnisch's ten largest holdings make up 100% of its $8.04B portfolio in Q2 2026.
- William Harnisch opened 1 new position and closed 2 in Q2 2026.
- William Harnisch's portfolio value rose 39% quarter-over-quarter to $8.04B.
Based on Peconic Partners's 13F filing for Q2 2026, filed 14 Aug 2026.