DAYTON, Ohio (AP) _ Ponderosa Inc. today ended its bid to thwart a takeover by New York investor Asher B. Edelman and accepted a sweetened, $29.25-a-share acquisition proposal from Edelman's investor group.

Edelman's group already owns about 1.8 million, or 18.5 percent, of the restaurant chain's 9.76 million common shares outstanding, and the total cost to acquire the remaining stock would be about $233 million.

On Dec. 2 Edelman had launched a tender offer to buy Ponderosa for $27.50 a share, an offer Ponderosa rejected as inadequate.

Under their new agreement in principle, however, Edelman will amend the tender offer to $29.25 a share. The agreement remains subject to approval by Ponderosa's board of directors.

In a statement Edelman said he ''has no current plans for any material changes in the business or operations'' of Ponderosa. He also said Gerald S. Office Jr., Ponderosa's chairman and chief executive, had agreed to stay with the company ''on an interim basis to insure a smooth transition.''

Ponderosa operates or franchises 631 steakhouses in the United States, Canada and Puerto Rico. It also operates 22 Casa Lupita restaurants and franchises three others in the United States, and it operates or franchises seven Steak & Salad restaurants overseas.

For the nine months ended Nov. 6, Ponderosa earned $13 million on revenue of $380.6 million.