Mainstream Capital Management
COST icon

Mainstream Capital Management’s Costco COST Stock Holding History

Mainstream Capital Management’s Portfolio COST Stock Details COST Fund Activity
Bought
Maintained
Sold
Quarter Market Value Status Shares Change in
Stake 		Trade Value Portfolio Weight Portfolio Position
2026
Q3 		$2.14M Buy
2,347
+24
+1% +$22.4K 1.26% 22
2026
Q2 		$2.17M Sell
2,323
-5
-0.2% -$4.98K 1.31% 21
2026
Q1 		$2.32M Buy
2,328
+1
+0% +$975 1.56% 15
2025
Q4 		$2.01M Sell
2,327
-57
-2% -$51.7K 1.31% 21
2025
Q3 		$2.21M Buy
2,384
+104
+5% +$100K 1.47% 19
2025
Q2 		$2.26M Sell
2,280
-2
-0.1% -$1.99K 1.64% 14
2025
Q1 		$2.16M Buy
2,282
+106
+5% +$103K 1.71% 11
2024
Q4 		$1.99M Buy
2,176
+15
+0.7% +$13.9K 1.4% 15
2024
Q3 		$1.92M Buy
+2,161
New +$1.88M 1.63% 15

Other funds holding COST

Swedbank
Swedbank Stockholm, Sweden $118B AUM 40.52% 1-Year Est. Return
Emerald Advisors
Emerald Advisors Bellevue, Washington $781M AUM 4.78% 1-Year Est. Return
Parnassus Investments
Parnassus Investments San Francisco, California $33.8B AUM 31.08% 1-Year Est. Return
Assenagon Asset Management
Assenagon Asset Management Senningerberg, Luxembourg $103B AUM 40.17% 1-Year Est. Return
New York State Teachers Retirement System (NYSTRS)
New York State Teachers Retirement System (NYSTRS) Albany, New York $52.9B AUM 36.03% 1-Year Est. Return
TD Waterhouse Canada
TD Waterhouse Canada Toronto, Ontario, Canada $38.4B AUM 30.28% 1-Year Est. Return
Cardano Risk Management
Cardano Risk Management Rotterdam, Netherlands $18.2B AUM 38.97% 1-Year Est. Return
Loring Wolcott & Coolidge Fiduciary Advisors
Loring Wolcott & Coolidge Fiduciary Advisors Boston, Massachusetts $10.8B AUM 9.05% 1-Year Est. Return
Asset Management One
Asset Management One Tokyo, Japan $40B AUM 30.45% 1-Year Est. Return
Ninety One (UK)
Ninety One (UK) London, United Kingdom $45.5B AUM 15.2% 1-Year Est. Return

Mainstream Capital Management's COST Position: Q3 2026 in Review

Mainstream Capital Management increased its Costco (COST) stake by 1% in Q3 2026, buying an estimated $22.4K and bringing the position to 2,347 shares worth $2.14M. The position accounts for 1.26% of the portfolio, ranked #22.

Mainstream Capital Management first reported a position in COST in Q3 2024 and has held it in 9 quarters since. The position peaked at $2.32M in Q1 2026. 1,591 funds tracked by Wall St. Rank hold COST as of Q3 2026.

  • Mainstream Capital Management held 2,347 shares of Costco worth $2.14M as of Q3 2026.
  • Mainstream Capital Management bought 24 Costco shares in Q3 2026, an estimated $22.4K.
  • Costco made up 1.26% of Mainstream Capital Management's portfolio in Q3 2026, its #22 holding.
  • Mainstream Capital Management first reported a position in Costco in Q3 2024 and has held it in 9 quarters since.
  • Mainstream Capital Management's Costco position peaked at $2.32M in Q1 2026.
  • 1,591 funds tracked by Wall St. Rank held Costco as of Q3 2026.

Based on Mainstream Capital Management's 13F filing for Q3 2026, filed 23 Oct 2026.