Restaurant Brands' share price lifted 19.4% in the month to $1.23.
Mr Young said the price had come from a low base but second quarter sales were up nearly 5% on the previous corresponding period (pcp) after being up 4.3% in the first quarter.
KFC continued to be the main driver of the improving trend for the company but Pizza Hut reported a second positive quarter.
"We have upgraded our forecasts in light of Restaurant Brands' positive first-half guidance."
Forsyth Barr had upgraded its valuation of the company by 16c to $1.55 a share.
Statistics assembled by Forsyth Barr showed Restaurant Brands was also the best-performed company for the year to date with its share price more than doubling in the period.
Other top performers in September were: ANZ's share price rose 12.7% to $29.65; Sky Network Television rose 10.1% to $4.74; Goodman Fielder rose 9.9% to $2.10; and Fletcher Building rose 8.4% to $8.35.
Mr Young said Fletcher Building was an interesting stock to follow.
It was performing well, against what the company thought it should be doing.
Fletcher Building started September at $7.75, rising to $8.35 before going ex-dividend this week.
It fell to $8.01 before clawing its way back to $8.50.
March 9 was the low for the NZX-50, which had steadily improved since then, he said.
The NZX gross index provided a 2% return for September, compared with a 6.2% return for the ASX 200.
"We officially came out of recession but it will be a slow grind out of the gloom. We will still have market volatility, like today, where the US was down exactly 200 points.
"We are coming into the US third-quarter reporting season soon and it will be interesting watching where that goes. The US has had a good period and we have piggy-backed on that. When they have good days, we follow."
The worst performers for September were: Fisher and Paykel Appliances, down 13.8% to 69c; NZ Refining, down 10.5% to $4.62; Rakon, down 9.4% to $1.25; Steel & Tube, down 9% to $3.95; and PGG Wrightson, down 8.6% to 64c.
