A distinguishing feature of the cognitive process of speech planning is its flexible balancing of speed, quality, and effort. Utterance planning strategies can vary adaptively depending on speaker goals and circumstances. For example, when speed is a priority, the planning process might sacrifice the quality of an utterance by engaging in more incremental, on-the-fly planning. A focus on utterance quality may require more time. But sometimes, speakers seem to plan utterances well in advance without sacrificing quality or speed. In this chapter, we focus on recent research that explores how working memory can foster the flexibility of speech planning strategies. We review the role that WM might play in individual levels of planning, including message planning, grammatical encoding (including lemma selection and structure building), and phonological encoding, and the extent to which the scope and quality of planning at these different levels could be subject to WM constraints or predicted by WM capacity. We conclude that WM is a (sometimes optionally invoked) part of a complex system of compensatory factors that can determine how speech planning unfolds.