Ventures operating under uncertainty face challenges defining a sustainable value proposition. Six longitudinal case studies reveal two approaches to business model development: focused commitment and simultaneous experimentation. While focused commitment positively affects initial growth, this commitment and lack of variety jeopardize long-term survival. Simultaneous experimentation implies lower initial growth levels, but facilitates long-term survival by enacting variety in a resource-effective manner. This article enriches organizational learning theory by demonstrating that not only distant search but also simultaneous experimentation results in variety. Moreover, simultaneous experimentation implies effectual behavior and reconciles the apparent juxtaposition between ‘action’ and ‘planning.’ Copyright © 2013 Strategic Management Society.